This invention relates to musical instruments, specifically to an improved sound post of which the ends adjust automatically to the inner surfaces of the vibrating plates on the top and back of stringed instruments. The invention also has an adjustable length.
A sound post in a violin or similar musical instrument is a supporting post which is friction fitted between the top of the instrument, beneath one foot of the bridge, and the back of the instrument. The exact position of a sound post in the violin family of musical instruments, its material, density, diameter, length, and closeness of fit with the inner surfaces of the top and back of the instrument, are crucial. They affect the quality of sound, playability, and physical health of the instrument. It requires a very high degree of skill to cut and fit a sound post to exactly the right length and have the ends fit precisely.
The sound post is cut and fit with no strings on the instrument. This allows for ease of viewing and judging the correct length. The instrument is then strung and brought to pitch.
The sound box of the instrument, comprising the top, back and sides beneath the bridge, undergoes distortions when it is brought to pitch. These distortions are well known in the art. They are small and not clearly visible to the naked eye but easily measured in the laboratory. When string tension changes, such as when changing brands or thickness of strings, the degree of distortion changes. Additionally, as the sound box is made of thin wood under high stress, daily fluctuations in temperature and humidity are sufficient to change the shape of the sound box and thus the degree of distortion.
It is also common practice to adjust the position of the sound post for optimum tone and playability. This can only be done after the instrument is playing and requires that the sound post be tapped to various positions, searching for the exact spot which gives the qualities desired by the owner. Obviously, once the sound post is moved from its original position it cannot fit the same.
The sound post which fits perfectly on the repairman's workbench soon fits less than perfectly because of use and atmospheric changes. And occasionally we find a sound post which could never have properly fit any instrument. It has been estimated by colleagues in the violin business that 75% to 95% of all sound posts do not fit properly.
Numerous patents have been issued to improve the sound post. Few, however, have directly addressed the critical fit of the ends to the inner surfaces of the top and back. A few patents, such as U.S. Pat. No. 322,925 (I. Hall, 1885 July 28), U.S. Pat. No. 547,150 (G. Monson, 1895 October 1), and U.S. Pat. No. 2,162,595 (G. Virzi, 1939 June 13) use padding to alleviate the mismatch. Besides muffling the sound, padding will not ensure full, even contact. The padding compresses more where there is more pressure, but there is still more pressure at those points. The padding evens out pressure variations somewhat but there is not full and even contact. U.S. Pat. No. 1,788,745 (S. Rowland, 1931 January 13) has a swivel mechanism but the device moves in only one plane, exactly as a screw "swivels" as it turns in or out. It does not move in more than one plane as is necessary to ensure full and even contact. U.S. Pat. No. 2,141,735 (A. Borg, 1938 December 27) has a pivot point but it is a locating pin and nothing pivots about it.
Several attempts have been made to adjust the length of the sound post. Several, U.S. Pat. No. 322,925 (I. Hall, 1885 July 28), U.S. Pat. No. 547,150 (G. Monson, 1895 October 1) and others, involve drilling holes through the top or back of the instrument. Such solutions are acceptable primarily to the patent holder.
To date no one has devised a sound post with ends which automatically fit the inner surfaces of the top and back, is easily adjusted for length by virtually anyone familiar with the art, which uses the traditional tools for installation and adjustment, and which does not appear unusual or strange to the player. It is an object of the present invention to provide an improved sound post which provides those features, as well as other advantages.
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing descriptions of it.
Accordingly, the invention provides a sound post for fitting between interior surfaces of a sound box on a stringed musical instrument. The sound post comprises a post having opposed ends, at least one end having a swivel platform with a flat surface thereon. The swivel platform allows the flat surface to be fitted against an interior surface of the sound box and to make full and even contact with the interior surface. In its preferred form, the invention provides a post with swivel platforms on each end. The swivel platforms can be swiveled in a plurality of planes to evenly contact the interior surface of the sound box. The length of the post is selected to frictionally fit the post between interior surfaces of the sound box with the flat surface on each swivel platform making full and even contact with the interior surfaces. A system for adjusting the length of the sound post is also provided.